Trace fossils as indicators of environmental change in Holocene sediments of the Archipelago Sea, northern Baltic Sea

Biogenic structures in Holocene sediments from the Archipelago Sea, northern Baltic Sea, were characterized through the analysis of X-ray images of four cores collected from water depths between 32 and 66 m. In the area, initial colonization of endobenthic invertebrates occurred at 7800 ± 80 calendar years BP. The trace assemblage at this level is low-diversity, small-diameter, shallowly tiered, and Palaeophycus-dominated; rare Arenicolites are also observed. Early colonization coincides with increasing marine influence in the post-glacial lacustrine setting just before the dramatic onset of brackish-water conditions established after 7600 BP. The post-incursion brackish-water assemblage possesses a higher diversity of traces (Planolites, Arenicolites, Lockeia, Teichichnus), which is taken to reflect the enhanced salinity and trophic state of the basin. The shift from Palaeophycus-mottling to a Planolites-dominated fabric represents changed behavioural patterns in the endobenthic community due to changed substrate properties. The ethology of the succeeding trace assemblage also represents a switch from domicile-based activities, such as predation, scavenging and interface-dominated deposit feeding to shallow-tier deposit feeding. Finally, traces are excluded from thinly laminated intervals, demonstrating that seafloor oxygen deficiency commonly reached levels that were detrimental to colonization of the sediment substrate.     

Mass mortality of macrobenthic communities in the lagoon of Hikueru atoll (French Polynesia)

Epibenthic macrofauna communities (corals, molluscs, echinoderms, and macroalgae) were investigated at Hikueru Atoll, Tuamotu Archipelago. The very low diversity and abundance that we observed (1 coral genus, and 2 mollusc, 1 echinoderm, and 17 macroalgal species) is likely to be the result of a mass mortality event that occurred 18 months earlier. Hydrological surveys suggest that this high mortality was the result of a major dystrophic crisis. Other atoll lagoons in the Tuamotu Archipelago have also been affected by high mortalities in the past, but Hikueru appears to have been the most frequently and intensely affected. The present study confirms that mass mortalities associated with phytoplankton blooms may be one of the major disturbances affecting coral reef ecosystems. Accepted: 14 May 2000     

Genetic assessment of captive Chinese water deer populations in Zhoushan Archipelago,China

Chinese water deer is a rare and vulnerable animal in China because of the poaching for medical use and the habitat loss. In this study, the genetic diversity and population genetic structure of 40 Chinese water deer from three populations in Zhoushan Archipelago were investigated with ten highly polymorphic microsatellite loci, including 4 screened from the nuclear DNA in the study, and 6 selected from the literature. According to the results, these captive populations had a higher genetic diversity than other rare cervid species, such as forest musk deer. No signs of inbreeding were detected. Low genetic differentiation among these populations was found. The probable reasons included the isolation by distance, the exchange among islands, or the supplement of the wild Chinese water deer. We proposed the deer raisers to strengthen the exchanges from different islands or mainland, and if possible, some deer would be returned to the wild to expand the wild population.     

Trait and phylogenetic diversity provide insights into community assembly of reef‐associated shrimps (Palaemonidae) at different spatial scales across the Chagos Archipelago

Coral reefs are the most biodiverse marine ecosystem and one of the most threatened by global climate change impacts. The vast majority of diversity on reefs is comprised of small invertebrates that live within the reef structure, termed the cryptofauna. This component of biodiversity is hugely understudied, and many species remain undescribed. This study represents a rare analysis of assembly processes structuring a distinct group of cryptofauna, the Palaemonidae, in the Chagos Archipelago, a reef ecosystem under minimal direct human impacts in the central Indian Ocean. The Palaemonidae are a diverse group of Caridae (infraorder of shrimps) that inhabit many different niches on coral reefs and are of particular interest because of their varied habitat associations. Phylogenetic and trait diversity and phylogenetic signal were used to infer likely drivers of community structure. The mechanisms driving palaemonid community assembly and maintenance in the Chagos Archipelago showed distinct spatial patterns. At local scales, among coral colonies and among reefs fringing individual atolls, significant trait, and phylogenetic clustering patterns suggest environmental filtering may be a dominant ecological process driving Palaemonidae community structure, although local competition through equalizing mechanisms may also play a role in shaping the local community structure. Importantly, we also tested the robustness of phylogenetic diversity to changes in evolutionary information as multi‐gene phylogenies are resource intensive and for large families, such as the Palaemonidae, are often incomplete. These tests demonstrated a very modest impact on phylogenetic community structure, with only one of the four genes (PEPCK gene) in the phylogeny affecting phylogenetic diversity patterns, which provides useful information for future studies on large families with incomplete phylogenies. These findings contribute to our limited knowledge of this component of biodiversity in a marine locality as close to undisturbed by humans as can be found. It also provides a rare evaluation of phylogenetic diversity methods.     

Spatial distribution patterns of Sargassum horneri in the coastal waters of the Ma'an Archipelago

Seaweed beds are a nearshore marine ecosystem composed of macroalgae and other marine organisms. In recent years, soil erosion, pollution, and other land-based mechanisms have severely reduced nearshore algal populations, particularly in areas influenced by the outflow of the Yangtze and Qiantang rivers. The Ma'an Archipelago is located in the estuary of the Yangtze and Qiantang rivers in the East China Sea. Although the archipelago is relatively distant from the shore, algal populations there have decreased significantly in recent years. The reasons for this decline are unknown, owing to an absence of data on macroalgal spatial distribution in seaweed beds and of long-term monitoring. Numerous environmental factors, operating at different scales, are likely to contribute to the abundance and distribution of macroalgae in seaweed beds. Therefore, it is important to study the beds across spatial scales to understand the ecological factors influencing the beds' presence and decline. During September 2014 and May 2015, we investigated the distribution of Sargassum horneri in germling and adult stages at 12 sites on three islands (Zhongkui, Lvhua, and Gouqi) around the Ma'an Archipelago. Our results showed that: (1) on a whole-archipelago scale, S. horneri density was highest around Zhongkui Island, and lowest around Lvhua Island. Adult plant lengths showed the opposite trend. The ratio of average densities around the three islands was 1 (Lvhua): 3.8 (Gouqi): 13.8 (Zhongkui) at the germling stage, and changed to 1:1.8:4 at the adult stage. (2) At the individual-site scale, wave exposure may explain why S. horneri density is highest in southeastern sites and lowest in northwestern ones. Around Zhongkui Island, S. horneri grew in turbulent conditions, was significantly affected by wave motion, and suffered a high mortality rate between the seedling and adult stages. (3) Within site scale, S. horneri was distributed over a considerably wider depth range around Zhongkui Island than around Lvhua or Gouqi islands. Adult S. horneri was most abundant at 2-m depth. Wave action apparently controlled the upper limit of S. horneri bathymetric distribution, whereas the lower limit depended on sedimentation and light availability.     

Activity rhythms of the shallow-water octopuses Octopus laqueus and Abdopus aculeatus with special reference to its relation to light and tidal cycles

Patterns of activity and inactivity were experimentally measured for two shallow-water octopuses, Octopus laqueus (n = 8) and Abdopus aculeatus (n = 4), inhabiting the Ryukyu Archipelago. Octopuses that were collected from the coastal waters of Okinawa Island were held in experimental tanks under controlled light conditions (L, light; D, dark; 12L:12D, LD conditions; 12D:12D, DD conditions). Behaviors of these two species were continuously recorded for 9 to 10 days. Under LD conditions, O. laqueus were active for 7 to 14 min during daytime and 298 to 339 min at night, and under DD conditions, for 97 to 140 min during daytime and 71 to 169 min at night. A. aculeatus were active for 49 to 99 min during daytime and 138 to 185 min at night under LD conditions, whereas under DD conditions, they were active for 36 to 56 min during daytime and 55 to 154 min at night. Continuous duration for activity cycles was 39 ± 7.6 h under LD conditions and 42 ± 2.6 h under DD conditions in O. laqueus, and 38 ± 7.4 h under LD conditions and 42 ± 2.8 h under DD conditions in A. aculeatus. Ratios for active duration to inactive duration did not differ between LD condition and DD condition both in O. laqueus and A. aculeatus.     

Spatial structure of coral reef fish communities at Kudaka Island (Ryukyu Archipelago), Japan

The present study aimed to investigate the spatial structure of fish communities at juvenile and adult stages on coral reefs at Kudaka Island (Ryukyu Archipelago, Japan) and to relate spatial patterns in the structure of the fish communities to gradients in environmental variables. Diurnal visual censuses allowed us to record 2,602 juveniles belonging to 60 species and 1,543 adults belonging to 53 species from October to December 2005. The distribution of species highlighted that the juvenile community was organised into three distinct assemblages, rather than exhibiting gradual change in community structure along the cross-reef gradient. Correlations between spatial patterns of juvenile community and environmental variables revealed that the most significant factors explaining variation in community structure were coral rubble and coral slab. In contrast, the adult community was organised into one assemblage, and the most significant variation factors in community structure were depth, live coral in massive form, live coral in branched form, dead coral and sand. Overall, the present study showed that most juvenile and adult coral reef fish at Kudaka Island exhibited striking patterns in their distribution and depth and some biological factors (e.g., abundance of live coral, dead coral and coral rubble) might exert considerable influence on the distribution of fishes.     

Conservation status and ex situ cultivation efforts of endemic flora of the Juan Fernández Archipelago

Was realized field studies and ex situ propagation on the vascular flora of Juan Fernández Archipelago during 15 year period. To evaluate the conservation status of a total of 133 species and subspecies of vascular endemic plants I used a IUCN classification founding: 2 species extinct, 1 extinct in it natural habitat, 52 critically endangered, 37 endangered and 9 vulnerable. Thus, 73.8% are contained in a threat category; only 24 taxon can be considered to be of a lesser conservation concern. The largest threat of extinction is a reduction in individuals in local populations resulting in small, isolated populations. This habitat fragmentation and a reduction in endemic flora has also impacted endemic fauna. Besides, during this period was propagated in nurseries a total of 80 of these species and subspecies (60%). It seem clear the necessity to continue to actions conserve this particular ecosystem.